Steam heating system



H. G. THOMAS 2,060,265

STEAM HEATING SYSTEM Npv. 1o, 1936.

Filed April 22, 1929 5 Sheets-Sheet 1 W ,/5 jim@ NOT'. 10, 1936. H GTHOMAS 2,060,265

STEAM HEATING SYSTEM Filed April 22, 1929 5 Sheets-SheeiI 2 7&7 79

Nov. 10, 1936. 'H. G. THOMAS STEAM HEATING SYSTEM Filed April 22, 1929 5ShQObS-Sheei 3 Nov. 1o, 1936. H G THOMAS 2,060,265

STEAM HEATING SYSTEM Filed April 22, 1929 5 sheets-sheet 4.Nv.`1o,'1936. HGTHOMAS 2,060,265A

STEAM HEATING SYSTEM Filed April 22, 1929 5 Sheets-Sheet 5- sun, wind,'and the like.

Patented Nov. l0, `v1936 UNITED STATES PATENT OFFICE STEAM HEATINGSYSTEM HerbertG. Thomas, Evanston, Ill., assignor to Webster Tallmadge &Compa Inc., East Orange, J., a corporation of New York vApplicationApril 22, 1929, Serial No. 357,034

` ss Claim. My invention relates to steam'heating systems and the like.

While the invention is particularly applicable to systems operating withcontrolof heat emis- Obviously, the rate of loss varies with the type ofbuilding but after that factor is once determined'it may be assumed tobe a constant and the above principle is varied only by such factors as'Ihe function of the heating system is to supply heat in just suiilcientquantity to make up for the loss so as to maintain the insidetemperature at substantially a predetermined value, 6r schedule ofvalues.

Fractional Vfilling of the radiators 'means the variation of the volumeof steam in the radiators. Heat emission is controlled by varying thevolume of steam at substantially constant temperature and pressure. Suchvariable filling is secured by interposing a flow controlling orificebetween the point of steam supply and the radiator, preferably anindividual orifice is supplied for each radiator. Now if the steam mainsare of adequate size, the Vpressure upon the supply side of the orificeis equali'zed upon all of the orifices of .a groupl of.

radiators. The return line is kept at suitable pressure, which may beatmospheric or above or below atmospheric. Preferably the returnpressure is kept below atmosphere for ease in circulating 'the steam;lparticularly at the lower flows. The return line pressure may be kept aconstant by a suitable governor which may be adjustable under thecontrol of the engineer in charge.

The supply' pressure is varied within a range lying between the returnline pressure for zero heat demand, as when the outside temperature isat 70 F., to a maximum for maximum heat demand for which the system isinstalled. 'I'he maximum heat demand in this region should be calculatedon the basis o f at least 10 below z`ero Fahrenheit.

Obviously, when the pressure differenceupon the opposite sides of theorifice is zero the flow is zero. l For maximum pressure difference uponthe orice the flow is a maximum. This rate of flow is designed to equaland not substantially vary from the maximum demand rate `of condensationof steam in the radiators corresponding to maximum heat demand and afilled radiator. 5

vSince the flow 'is accurately predetermined and Vdoes not depend uponthe temperature of the medium surrounding the radiator,the rate ofcondensationv is not perceptibly increased by lowering the temperatureof the medium Asurroundl0 ing the radiator. The radiators should be ofsumcient capacity that. for normal inside temperature of, for example,F. the radiator will be filled upon maximum demand for heat. Obviously,a margin is desirable. Steam traps are not .l5`

essential to the normal operation of a system of A this character butpreferably are employed to prevent the flow of steaminto the return mainfor any inaccuracy in design or installation.

Such av system for full realization of the ad- Q0 vantages thereofshould'be automatic in character u to the extent of having the heatemitted by the radiators governed in accordance with the difference intemperature between the inside of the Y room, which is preferably keptat a predeter-Jg mined value for normal operation, and the vari ableoutside temperature.

There are special circumstances such as sun,

wind, and the like, which cause variations of the loss of heat from thebuilding which the heating a0 systemvis designed to replace so as tomaintainva uniform inside temperature.

The chief difficultyin making the heat emission of the radiatorsresponsive to the temperature difference or weather conditions is thefact that thermostatic means may readily. be developed' to be directlyresponsive to temperature difference or to temperature but there is nosimple way to control heat emission as a linear function of temperatureor temperature difference. 40

The law relating to flow'of fluid through an oriflse is substantiallyV2=2gh where V is velocity of flow, g is the acceleration due togravity, and h represents head or pressure difference upon the orifice.From this it will be apparent thatthe 45 variable h or pressuredifference upon the orifice must be controlled not in equal incrementsfor equal increments of heat demand or temperature difference, but inunequal increments varying .according to the square root of theincrements of 50 temperature difference.

My invention aims to provide a simple mechanism between athermostatically responsive element and a control valve forautomatically varying heat emission as a function of temperature 55difference. While I speak of a control valve as being the controllingelement for varying the heat emission, I do not intend to be limited toa valve but may employ any equivalent mechanism which acts to secure apressure difference upon the orice.

For conditions of sun, wind and the like, it is often desirable to varythe percent of load in accordance with the percent variation of heatloss which such conditions make. For example, if one side of thebuilding is exposed to the sun, the rate of heat demand therein isreduced, and it is desirable to cut down the rate of heat ow. On awindyday it may be desirable to in crease the heat flow from the radiatorsabove the normal rate. In large buildings it is advisable to divide thebuilding into heating zones and operate the zones on different rates ofheat emission.

Where the ratio between thermostatic action and steam pressure is acurve, as above explained, it is not a simple matter to increase ordecrease the heat output throughout the range.

My invention aims to provide simple and effective means to vary thepercent of normal load either by hand .adjustment or by automaticadjustment. My invention also provides a manually controlled adjustmentfor varying the percent load in accordance with its heating schedule as,for example, day and night or holiday service, and also provides meansfor increasing the rate of heating as, for example, in bringing thebuilding up to the normal working temperature.

The preferred form of the invention involves the use of a cain ascontrolling the relation between the thermostatic response and pressuredifference variation, and a lever system having a movable fulcrum tochange the percent of load of heat delivered. The cams may be directlyoperated or may be operated through remote control mechanism or throughthe use of relayed power.

The changein position of the cam follower may be translated into termsof movement of a valve or other controlling mechanism through electric,electro-pneumatic or electro-'hydraulic or .other I do not intend to belimited to the use of the cam as embodying the flow equation as anelectric resistance might be employed to embody such relation. i

Now in order to acquaint thoseskilled in the art with the manner ofconstructing and operating. a device embodying my invention; I shalldescribe in connection with the accompanying drawings a specinc form ofapparatus embodying my invention.

In the drawings:

Figure 1 is a diagram of a steam heating system embodying my' invention;

Figureisaticshowingofthe control mechanism;

Figure 3 is a modified form of control mechanism shown diagrammaticallyas in Figure 2;

Figure 4 is a side elevation partly in section o! a tbennostatic elementembodying sun and wind controls which thermostatic element may beemployed in connection with the system shown in Figures 1, 2 and 3;

Y Figure 4A is a top plan view of the thermostat body shown in Figure 4;

Figureisapartialdiagramofasystem having an electric relay controlbetween the thermostats andthevalvecontrolling.

Referrlngnowtoli'lgureLasteamsupply mainIprovldesstmatanydesiredpressureforuse in the heating system having theradiators 2, 2. The steam main I is connected to the supply main 3through a control valve 4, which is of any suit able type forcontrolling the rate of flow Afrom the main I to the supply main 3 inorder to regulate the pressure Vin the supply main 3.

The valve 4 may be merely a throttle valve or it may be a pressurereducing valve variably loaded to control the pressure prevailing in thesupply main 3. This valve 4 is suitably controlled by a reversible motor54 which, under thermostatic control, suitably governs the valve l tomaintain a pressure in the supply main 3 representing either a desiredabsolute value or a desired differential with 'respect to the pressurein the return main 6. The radiators 2, 2 are connected to the supplymain 3 through suitable orifices contained in the valves 1, 1. Thesevalves 1, 1 preferably contain oriiice plates for interposing oriflcesof predetermined size between the supply main 3 and the in-` terior ofthe radiator. The valves 1, 1 permit the selection of a suitable size oforifice within the control of the operator. In lieu of such modulationvalve 1, 1 xed orifices may be provided over which the. occupant of theroom has no control.

The valves 1, 1 or the orifices which may be substituted for them areinterposed between the branch lines such as 8 and 9 and the radiators,these branch lines being supplied from the supply main 3. The radiators2, 2 are connected through the traps I0 to return pipe I I whichconnects with the return main 6.

`The thermostatic traps III, III are of known construction and areadapted to shut off the radiators from the return connection in casethey are impinged by steam in order to prevent loss of steam eitherthrough overload of the radiator or through any error in design orinstallation of theradiator, and also to prevent loss of steam when theradiators are completely filled.

The return line 6 is preferably connected to a vacuum pump provided witha suitable governor for maintaining a predetermined pressure belowatmosphere in said return main i. It is not essential to keep the returnmain below atmosphere as it may be an open return main, that is,operated at atmospheric pressure, if desired.

The motor 5 which controls the valve l is in turn controlled by agoverning mechanism I2 shown in Figure 1 as disposed upon the roof I3 ofthe building. This governing mechanism comprehends a thermostat Il and apressure conveying tube I4 leading from the control element I2 to thesupply main l, and a pressure conveying tube I5 connecting the controlmechanism I2 with the return main l. The control mechanism I2 is underthe control of a manually operated variator I1 located at` the stationof the engineer or attendant, the varlator I1 functioning to control thepercent loading of the heating syst'em, as willA be more apparent later.

The control mechanism is illustrated diagram,- rnatically more in detailin Figure 2 and a modiilcation thereof in Figure 3.

A control cable Il connects the variator I1 with the control mechanismI2 for remote control, and the cable I8 connects the motor i oi the lpressure control valve I with the control devi I2.

Referring now to Figure 2, the thermostatic element I3 consistspreferably of a chamber one wall of which is movable under the expansionot a contained liquid such as alcohol, or the like. said movable wallbeing connected through a rod 2l to the short arm of a lever 22 pivotedat 23 to the stationary frame 24. The`operating'rod 2I includes anadjustment 25 for coordinating the setting of the thermostat I3 with thecam 26. The long arm of the lever 22 is connected through a link 21 to arack 26, which rack cooperates with a pinion 29on the shaft 3B whichbears the cam 26. The rack 28 is suitably guided asffor example, by theroller 3I to maintain its mesh with the pinion 29. By this connectionmotion of the movable wall of the thermostat I3 istransmitted intorotary motion 'of the cam 26 to adjust the cam to a positioncorresponding to the expansion or contraction vof the thermo-- staticelement I3 under thev prevailing outside temperature.

A cam follower consisting of a slidable rod 33 guided in suitable guidessuch as 34, 35 cooperates with the cam 26 to rock the lever 31` whichhas anadjustable pivot 36 mounted upon a standard 39, said standard orbracket being in turn mounted upon the slide member 40 guided insuitable guides such as 4I, 4I.

The opposite end of the lever 31 is connected to a rod 43 containing anadjustable connection 44 to the lever 45. v'I'he lever 45 is pivoted atits central .portion on the pivot '42,said pivot being connected toa(suitab1e frame member.

The lever 45 carriesA a pair of contact members 46 and41 mounted uponrods such as 48, these rods being pivotally connected to .the ends ofthe lever 45 so that for a given angular or rocking movement of thelever 45 one of the contacts 46, 41 will be moved'up and the other willbe moved down a like amount, or vice versa.

vThe rods 4I?v pass into the legs or chambers 50 v 4 is a reversiblemotor, having one lead 54 connected to the contact `46 and so related tothe body of mercury, which bodyoi mercury is conneoted through -the wire56 to the common wire applied as a cam follower.

ofthe motor 5, that if the contact 46 electrically connects with thebody of mercury corresponding to too high a` differential of 'pressureupon the iiow controlling orifices 1, the motor will be operated toclose or throttle down the valve 4, whereas the contact 41 and its lead55-are so related to the body of mercury that if the pressuredifferential is notas great as is called for by the thermostat I3,contact will be made between the contact member 41` and the body ofmercury 53 resulting in operation of the motor 5 to increase the openingof the valve 4 or otherwise to raise the pressure in the inain'3.

Referring now to the slide 40 bearingthe adjustable pivot standard 39and the adjustable pivot 3B, it is to be noted that this slide is underthe control of a cam member 60 to which it is A- suitable spring may beapplied to the slide 40 for causing it to follow the contour of the cam60. The cam 60 is adjusted in accordance with the desired percentage ofsteam load which the radiators are to carry. That is to say, -`assumingthat the cam 60 is in the position shown in Figure 2, the .position ofthe,slide 40 corresponds to ,100% steam load which under normalconditions will maintain the rooms in which radiators 2, 2 are containedat the predetermined temperature which may, for example, be '70 F.

If now the cam 60 is rotated in a clockwise direction, it will be seen.that movement of the slide 40 to the right, as viewed in Figure 2, willresult in a change inratio'of the two arms of the lever 31 and also du'eto its motion in the horizontal line will cause a raising of the righthand vend of said lever 31 vwith a consequent change in counterclockwise direction resulting in travel of the slide 40 tothe left, asviewed in Figure 2, will result in dropping the contact 41-and raisingthe contact 46 which calls for a higher pressure differential upon theradiator orifices.

It is to be noted that the cam 26 might be operated by hand inaccordance with the action ofthe thermostat or thermometer correspondingto the thermostat I3 although I have shown, and

prefer, automatic operation. Likewise, it is to be observed that the cam60 may be directly operated by hand, or as I have shown the preferredconstruction, it may be operated from aremote control station by meansof the variator I1. The cam 26 preferably embodies the relationAbetween, equal increment of temperature change at the thermostat I3 andunequal increment of pressure change in the supplyline 3 to secure equalincrement of heat delivered or heating fluid delivered through theorifices into the radiators.2.

The cam 60 embodies merely the proportionality between the twoends ofthe lever 31. That is to say, a predetermined motion of the cam 60results in a predetermined percentage of normal loading of the heatingsystem exemplified by the' radiators 2. That is to say, if the cam 66 isset to deliver say 150% heating load, as for heating upr the buildingrapidly, or for an unusual' condition of weather corresponding to windcondition, the' proportionality of movement throughout the range of thecam 26 is changed to such 150%.

Now it is to be observed that when the thermostat I3 stands at the zeropoint of heat load, that is, for example, 70 outside, the lever 31 willbe strictly parallel to the guides 4I, that isl horizontal4 as viewed inFigure 2. Under that condition the pressure diierence control element 43should be subjected to zero pressure difference andthe orifices shouldbe' subjected to zero pressure difference, and the contacts 46 and 41should, likewise, be horizontal and bothl out of Contact with themercury 53. Nowany change of position of the cam 60 corresponding tozero heat requirement effects no change in the steamA demand. This isobvious, for 150% of zero load is no different than 100% of zero load.Hence it will be seen that the cam' 60 and slide 40, which constitutesthe cam follower' for cam 60, `change the percentage loading at any.given setting equally throughout the entire load curve.

Likewise, if the cam 60 be rotated in a clockwise direction when thedemand for heat is zero, a '75% load requirement when the'demand is'zero will not change conditions since 75% of zero load is zero.Likewise, the load curve will be changed to correspond to '75% loadthroughout the entire load curve.

The means I have shown for operating the cam 60 from the remote controlstation I1 includes an operating motor 64 driving through a worm gearconnection 65, the shaft 66, which in turn operating through a worm gearconnection 61 and worm wheel 68. moves the cam 60 forward or reverse.The cam 60 is connected to a contact member or selector contact 10cooperating with a bank of contacts 1|, this bank of contacts beingconnected through the cable i8 with a cooperating bank of contacts 12 atthe control station. The bank of contacts 12 is adapted to be engaged bythe two contact sectors or plates 13 and 14 separated from each other bythe distance of one contact and a pointer 15 lying in line with the gapbetween the sectors 13 and 14 to indicate the position of the contactsectors 13 and 14. A suitable hand wheel 16 is provided for operatingthe contact making mechanism.

The selector contact 10 on the cam 60 is connected to the common returnwire 11 leading to the motor 64 and the contact sectors 13 and 14 areconnected through the control wires 18, 19 to the motor 64.

Now it can be seen that by moving the control wheel 16 to throw thepointer 15 to one side or the other from its central, or 100%, position,the motor will be energized to shift the cam so that the linger 10 stopsupon the deenergized contact in the bank 1| corresponding to theposition of the finger 15 in the variator I1.

Any other suitable form of remote control might be provided.

In Figure 3 I have shown a modified form of the device in which insteadof circular cams 26 and 60, I provide the cams and 8| having rectilinearmotion. Otherwise the construction is the same. The link or rod 21instead of being connected to the circular cam, as shown in Figure 2, isconnected through a bell crank 82 to the rectilinear cam 80. The bellcrank 82 is pivoted at 483 and the longer arm is connected through a pinand slot connection 84 to' the rectilinear cam 88 which cooperates withthe cam follower or rod 33. The cam 88 is shown as graduated for thetemperatures corresponding to the load curve'of the system. 'I'he lengthof the ordinates indicated by the vertical lines represents the pressuredifference required upon the orifices 1 of the radiators 2 to give equalincrement of iiow and hence equal increment of volume within theradiators 2 for equal increment of temperature change as registered onthe thermostat I3.

The same relation between the movable pivot 38 and its lever 31 prevailsin this form of thedevice, that is to say, when the point of the caxfollower 33 lies upon the ordinate corresponding to 70" on therectilinear cam 88, the arm 31 is horizontal and the two electriccontacts 48 and 41 are likewise horizontal and out o! contact with thebody o! mercury 58. The U-tube 82 is provided with adjusting screws 51,81 molmted on the supporting frame 88 for adjusting the position of saidelements. A'Ihe rectilinear slide 88 is guided in suitable guides 85, 88for maintaining the guided motion of the cam 88.

The cam 8-|likewise is mounted in guides 88, 88 for guiding the same ina predetermined-rectilinear path at right angles to the motion of theslide 48. ThecammemberIl isgraduatedin Figure 3, the load cam 8| is innormal or 100% load position. By raising the cam 8| less than normalloading, as for example on nightor holiday schedule, may be maintained,whereas if the cam 8| is lowered, higher than 100% load is to be carriedand will be maintained throughout the temperature range of the system.'Ihe same relation previously explained is maintained, that is to saythroughout the entire range of temperature variations for which` thesystem is designed the percentage of load required will be maintainedwhen the same is once adjusted at the cam 8|.

'Ihe cam 8| is operated by the rod 66' under the control of thetransmission 65' corresponding toA the similar rotary transmission inthe device of Figure 2, such transmission being operated by the motor 64in forward or reverse direction in order to secure motion up or down asdetermined by the position of the control handle and contacts of thevariator I1. The selecting contact ringer 10', which is connected to therectiiinear load cam 8|, cooperates with the bank of contacts 1| whichare arranged in the path oi movement of said contact selector ringer18'.

It will be understood that the cam followers are held in engagement withtheir cams by suitable spring means or the like.

In Figure 4 I have shown a type of thermostat which is sensitive at thesame time to sun and wind. This thermostat 90 comprises a tubular body9| mounted upon a suitable stem or tube 82 and containing an expansibleelement 83 filled with a liquid such as alcohol, or any other suitableliquid or fluid, and having a moving stem 84 extending through thehollow stem 82 of the casingl. The casing 8| may be open to atmosphereand to the sun.

The vertical and horizontal surfaces are adapted to be substantiallyproportional to the vertical and horizontal surfaces of the buildingwhich this thermostat represents. Thus it may be made accuratelyresponsive to sun conditions. That is to say, ii.' the sun strikes thetop of the same it has less area exposed to such radiant heat than wherethe sun strikes the same at an angle or sidewise.

The body or container 8| may be provided with three or more vanes, suchas 85, to render the same responsive to wind. Ii desired, a series ofthree dashpots may be disposed about the circumference of the stem 32 soas to steady the motion of the same under unsteady wind conditions.

'Ihe stem 82 which bears a movable thermostatic element has a sphericalconvex head 88 disposed within a spherical concave socket 81, a suitablespring such as 88 maintaining the two parts in engagement constituting aball and socket joint.

The thermostat stem 84 which passes through the body stembears a membersuch as the disc 98 at its lowerend within a circular boxlike couf plingmember |88, the flange of which rash against the top o! the disc 88. Thecoupling member or cage |88 is connected to the stem |8| which is guidedat |88 in the frame |88. The stem |8I isconnectedtothelever 22 whichmaybe identiiled with like part in Figures 2 and 3.

Thecage |88 andthediscareheldinengngoment with each other through thetension spring |84 which is suitably adjustable. The lever 82 is in turnconnected to the rod'21 which may be identiiied by reference to Figura 2and 3.

Nowitmaybeseenthatanofdxs termsofpercent of normal load. Asshmminmemherimdertheactlonofmn a thermostat which in its own structureprovides l `or hammer member |40 mounted upon a spring Apherctemperature or the suns heat results in a rise of the rod 21, and thisrod may be connected to the mechanism shown in Figure 2 or that shown inFigure 3, the result being a shifting of the contacts 46 yand 41 callingfor less pressure vdifference upon the Vorifices and, hence, less volumeof steam delivered to the radiators, and a smaller percentage of theradiator space filled with steam corresponding to less load.

In like manner, contraction of the thermostatic element 93 results inraising the rod |0| and a 1 depression of Ithe rod 21 and this, as willbe evident from either Figure 2 or Figure 3, results in an increaseddifferential upon the radiator orifices and an increased percentage ofthe radiator space filled with steam and a larger emission of steamcorresponding to the call of the thermostat.

Incidental wind pressure upon the side of the thermostat body from anydirection results in a rocking of the thermostat about the center of thespherical parts 96, 91 and hence a parting of the resulting in raisingof said cage and rasing of the rod |0| and a call for a greater pressuredifference upon the orifices and greater delivery of steam to theradiators.

It will be seen, therefore, that I have provided means responsivetovariable atmospheric temperatures, variable incident heat rays fromthe sun, and variable wind effect upon the building. As above explainedthe thermostat of Figure 4 may be applied to the system shownv in Figure1 and embodying the features of Figures 2 and 3.

In Figure 4A I have shown how the vanes 95 are applied to the body 9| toget substantially equal action from the wind in any quarter.

In Figure I have shown a remote control operating mechanism forelectrically transmitting the thermos'taticn control to the pressuredifference control mechanism 49.` In thiscase the mostat, its lever,contact arm and contact bank' with'the resistance |00 may be disposed onthe roof whereas the major part of the'thermostatc circuit |09 with theother apparatushere to be described may be disposed at the controlstation as, for example, in the basement of the building.

The resistance |08 may be connected through the control wires II 0running from theroof of the building to the basement where theWheatstone bridge circuit |09 is maintained. I'he two legs III and I|2of the Wheatstone bridge circuit |09 may be adjusted to proper values,for example, equal values, and the fourth arm of the bridge contains anadjustable resistance -,I I3 Vunder the control of a swinging contactmember I I4 mounted upon a shaft ||5. A variable resistance IIS whichmay control percentage of full load is connected in shunt of theresistance I|3 or so much of it as is *connected in the bridgecircuit.Itifiviu be observed that theresistance ||s acts like the variablefulcrum 38- in that for a position of the thermostat |05 correspondingto cold outside temperature the greater part of the resistance I I3 willbe included in the circuit and VVsulting in motion of the block |20 toeffect upon the circuit. The Wheatstone bridgecircuit |09 contains inits bridge connection, that is in series with the wires II1, the movablegalvanometer coil ||8 which contains a movable pointer 9 carrying ablock |20. When the bridge is, in balance the block |20 lies over theedges of the two gear sectors I2 I and |22 pivotally mounted at |23 and|24, said gear sectors being connected together through the pinion |25.-

The pinion |25 is connected through a rocking shaft |26 to a threecontact mercury bulb switch |21, the central contact of which isindicated at |28 and connected to the body of mercury, said body ofmercury when the bulb is tilted to one side or to the other makingcontact with the outer contact to close circuit from the common wire |29to either the forward orreverse wires |30 and |3| for the reversiblemotor |32. The reversible motor |32 is in turn connected through theshaft ||5 to the cam 26 and to the aforesaid movable contact ||4.

A cam follower 33 is connected to the rocking lever 45 of the pressuredierence control mechanism 49, which governs the operation of the motor5 for opening and closing the valve 4 to.4

control the pressure in the supply main 3 imposed upon the radiatororifices.

Cooperating with the block |20 is a presser arm |4|, said spring armbeing acted upon by cam |42 on the shaft |432 The shaft |43 isconstantlydriven at a uniform rate tending to depress the presser |40 whichpresser engages the block |20 iupon each downward stroke pressing theblock |20 which is mounted on the spring army ||9 downwardly. If thegalvanometer coil I|8 due to unbalance of the Wheatstone bridge circuit|09 springs the block |20 away from the neutral position sufliciently sothat upon the next downwardy motion of the presser |40 said block |20engages onlyone of the gear sectors |2| or |22 the result is a tiltingof the, mercury switch bulb |21 and closing ofthe circuit of the motor|32 to shift the position of the cam 26 and the contact ||4 in adirection to restore balance.

Instead of periodic motion of the presser block, the gear sectors I2||22and pinion |25 with connected parts may be swung up and down on a springarm uke the arm |4| the block |40' then remaining stationary. Also I mayemploy instead of the specific form of resistance varying thermostatherein shown, any preferred or known form of means responsive totemperature variation, for example a resistance thermometer of knownconstruction. l

Thus if the movement of the thermostat |05 is such as to shift thecontact |06 with respect to the resistance |08 so as to vary saidresistance, the Wheatstone bridge |09 will be unbalancedreor the otherand a consequent closing of the cir- "cuit of the motor |32 in adirection to restore Also, it will be apparent to those skilled in the'`art that instead of embodying the variable relation between positionsof the thermostat and positions of the pressure difference control con-6 one side 0 tacts 4B, 41 I may embody said equation in the relation vofthe resistances |08 and I I3. That is to say, equal steps of motion bythe thermostat |05 may cut out or cut in unequal steps of resistance onthe bank of contacts |01 with a corresponding motion of the shaft I I5to compensate for the same.

It will now be apparent that I have provided a system in which by simpleapparatus and mechanism the positions of the thermostat corresponding tovariations in outside temperature are translated into correspondingpercentages of filling of the radiators 2 and that means correspondingpercentages of maximum heat emission at the radiators 2.

It will also be apparent that I have provided a thermostatic meanssensitive to three variables which may be utilized in my system, or maybe utilized in other control systems, for -securing a heat delivery tothe building to maintain it at a predetermined temperature or scheduleof temperatures.

I have also provided a system in which a suitable remoteoperationmechanism may be interposed between the thermostat and thepressure diierence responsive mechanism, such as 49, located at apointremote from the same and this is done preferably through anelectrical connection. 'Y

It will be apparent also that I have provided in the several systemsherein shown means for varying the percentage of loading throughout theentire range of temperature differences for which the system'isdesigned.

In view of these fundamental features of novelty I do not intend tobe'limited to the precise details shown or described, and I consider itwithin the skill of the art both to embody in more mmercial form` than Ihave shown the teachings of my invention and to make such modificationsas are in accordance with such teachings without departing from thescope of my invention.

While I have described steam as the heating uid it is to be understoodthat I might use hot water and secure the variations of heat emission bycontrolling the temperature of the water or the rate of flow thereofthrough the radiators.

In the mechanisms shown in Figures 2 and 3, it is not necessary that acam be supplied for moving the slide 49, as this could be adjusted byhand if suitable graduation is provided to determine the` properposition for the movable pivot 3l for different desired percentages offull load.

It is to be understood that this system can be used with filledradiators in which the heat emission is controlled by varying thetemperature of steam within the radiators. In such case, preferably, aconstant differential between the return and supply is maintained by anelement which is suitably responsive to variations in supply pressurefor determining, the return pressure, and the supply pressure may becontrolled by mechanism such as indicated at 4! for governing thepressure in the supply main in accordance with a predetermined law.

The U-tube might have the contacts embedded in the walls or fixed in thewalls otherwise and the entire U-tube be tilted to raise and lower thecontacts with respect to the mercury instead of merely shifting thecontacts 48, 41 through thewallsof the U-tube.`

Such a U-tube mechanism might control the suction instead of thepressure, that is to say, the valve 4 shown as controlling pressuremight be a governing element controlling the suction in the return lineE.

Where separate controls 'of supply and retur pressure are to beprovided, more than one U- tube might be operated at the same time bythe lever, such as 31, and instead of comparing the pressures betweenthe return and supply, the pressure of either one might be determinedagainst an arbitrary standard such as a head of liquid or the like.

I claim:

1. In a system of the class described the combination of means forsupplying variable amounts of heating fluid to a building to be heatedin proportion to the varying diierences `between a predeterminedtemperature and the variable temperature outside of the buildingthroughout a given range of outside temperatures, said means comprisinga cam and cam follower, the relation of throw to motion of the camembodying the relation between pressure difference upon an orifice andthe rate of flow therethrough, and thermostatic means imparting motionto said cam. K

2. In a system of the class described the combination of means forsupplying variable amounts of heating fluid to a building to be heatedin proportion to the varying differences between a predeterminedtemperature and the variable temperature outside of the buildingthroughout l. given range of outside temperatures, said means comprisinga cam and cam follower, the relation of throw to motion of the camembodying the relation between pressure difference upon an orince andthe rate of flow therethrough, and means for selectively varying thepercentage of normal rate of ilow of heating fiuid throughout theaforesaid range of outside temperatures.

3. In a system of the class described the combination of means forsupplying variable amounts of heating fluid to a building to be heatedin proportion to the varyirm differences between a predeterminedtemperature and the varying temperature outside of the buildingthroughout a given range of outside temperatures, that means com prisinga cam and cam follower, the relation of throw of the cam follower tomotion of the cam embodying the relation between pressure differenceupon an orifice and the rate of fluid llow therethrough, and means forselectively varying the percentage of normal rate of flow of heatingfluid throughout the aforesaid range of outside temperature, said meanscomprising a cam and cam follower, the said second cam follower cooperating with the first cam follower.

4. In a system of the class described the combination of a thermostatresponsive to outside temperatures, means controlled by said thermostatfor supplying variable amounts of heating fluid to a building to beheated in proportion to the varying diierences between a predeterminedtemperature and the variable temperature outside oi.' the buildingthroughout a given range o1 outside temperatures, said means comprisinga cam and cam follower, the relation of throw of the follower to motionof the cam embodying the relation between pressure difference upon anorifice and the rate ofiluid flow therethrough, and thermostatic meansimparting motion to said cam.

5. In a system of the class described the combination of thermostaticmeans responsive to outside temperature, means controlled by saidthermostatic means for supplying variable amounts of heating fluid to abuilding to be heated in proportion to the varying dilerences between apretherethrough and means for selectively varying the percentage ofnormal rate of flow of heating fluid throughout the aforesaid range ofoutside temperatures, said means comprising a cam and a cam follower anda member for controlling the flow of the heating fluid governed by bothof.

said cam followers.

6. In combination radiators, orifices therefor, heating fluid supplymeans, heating fluidpressure controlling means between said supply meansand the radiators, a thermostat, a cam actuated by the thermostat, afollower for the cam, the relation of throw of the follower to themotion of the cam embodying the relation of pressure difference upon theorifices and the consequent flow therethrough, and means governed by thethrow of the follower for controlling -said heating fluid pressurecontrol means.

7. In combination radiators, orifices therefor, heating fluid supplymeans, heating fluid pressure controlling means between said supplymeans and the radiators, a thermostat, a cam governed by` the positionof the thermostat, a follower for the cam, the relation of throw of thefollower to the motion of the cam embodying the relation of pressuredifference upon the orifices and the consequent flow therethrough, meansgoverned Aby the throw of the follower for controlling said heatingfluid pressure control means, and means for selectively varying thepercentage of normal rate of flow of heating fluid throughout theaforesaid range of outside" temperatures, through which the thermostatis projected.

8. In combinationradiators, orifices therefor, heating fluid supplymeans, heating fluid pressure controlling means between said supplymeans and the radiators, a thermostat, a cam governed by the position ofthe thermostat, a follower for the cam, the relation of throw of thefollower to the motion of the cam embodying the relation of pressuredifference upon the orifices and the consequent fiowtherethrough, meansgoverned by the throw of thefollower for controllingsaid heating fluidpressure control means, and means for selectively varying the percentageof normal t, rate of flow f heating fluid throughout the aforesaid rangeof outside temperatures, through which the thermostat is projected,saidlatter means comprising a cam and a cam follower said last named camfollower cooperating with the means governed by the throw of the firstfollower.

9. In combination radiators, heating fluid supply means, heating fluidflow control means between said supply means and radiators, a thermo-rstat subject to outside temperatures, a cam governed by the position ofa thermostat, a follower for the cam, and a lever governed by the throwof the follower for controlling said heating fluid flow controllingmeans, a movable pivot for said lever and means for moving the pivot tovary the percentage of normal flow of heating fluid throughout the rangeof temperatures to which the thermostat is subjected.

10. In combination radiators, inlet orifices therefor, heating fluidsupply 'neans, heating fluid pressure controlling, means between saidsupply means and theradiator orifices, a thermost'at subject tooutsidetemperatures, a cam operated by said thermostat, a follower for the cam,the relation of throw of the follower to motion of the cam embodying therelation of pressure difference upon an orifice and the consequent flowof fluid therethrough, a lever controlled by said cam follower, andmeans governed by said lever for controlling said heating fluid pressurecontrolling means.

11. In combination radiators, inlet orifices therefor, heating fluidsupply means, heating fluid pressure controlling means between saidsupply means and the radiator orifices, a thermostat subject to outsidetemperatures, a cam operated by said thermostat, a follower for the cam,the relation .of throw of the follower to motion of the cam embodyingthe relation of pressure difference upon an orifice and consequent flowof fluid therethrough, a lever controlled by said cam follower, andmeans governed by said lever for controlling said heating fluid pressurecontrolling means, said lever having a movable pivot and means to movesaid movable pivot for varying I the percentage ofnormal delivery ofheating fluid ply means, heating fluid pressure controlling meansbetween said supply means and the radiators, a ythermostat subject tooutside temperatures, a movable cam the position of which is controlledby the position of the thermostat, la follower for the cam, a levercontrolled by said follower, means controlled by the lever for governingthe heating fluid pressure controlling means, said lever having amovable pivot, and means for adjusting said pivot to control thepercentage of normal fluid delivery to the radiators.

13; In combination radiators, heating fluid supply means, heating fluidpressure controlling means between said supply means and the radiators,a thermostat subject to outside temperatures, a movable cam governed bythe-thermostat, a follower controlled by the cam, a lever operated bythe follower, means controlled by the lever for governing said heatingfluid pressure controlling means, a movable pivot for the lever, and acam for controlling the position of the movable pivot.

14. In combination radiators, heating fluid supply means, heating fluid-pressure controlling means between said supply means and the radiators,a thermostat subject to outside temperatures, a movable cam governed bythe thermostat, a carn actuated by the thermostat, a follower for thecam, the relation between the throw of the follower and the motion of'the cam embodying the relation between pressure of the heating fluidand the heat to be emitted by the radiators, and means governed by thethrow of the follower for controlling said heating fluid pressurecontrol means.

l5. In combination radiators, heating fluidsupply means, heating fluidpressure controlling means between said supply means and the radiators,a thermostat subject to outside temperai heating fluid throughout therange of temperatures to which the thermostat is subjected.

I6. In combination radiators, heating fluid supply means, heating fluidpressure controlling means, a thermostat, a cam governed by the positionof the thermostat, a cam follower, the relation between the throw of thefollower and the motion of the cam embodying the relation betweenpressure of the heating fluid and the heat to be emitted by theradiators, means for selectively varying the percentage of normalpressure of heating fluid throughout the range of temperatures to whichthe thermostat is subjected, said means comprising a cam and a camfollower, the second cam follower cooperating with the first camfollower.

17. In combination radiators, heating fluid supply means, heating fluidpressure controlling means, a thermostat, a cam governed by the positionof the thermostat, a cam follower, the relation betweenV the throw ofthe follower and the motion of the cam embodying the relation betweenpressure of the heating fluid and the heat to be emitted` by theradiators, means for selectively varying the percentage of normalpressure of heating fluid throughout the range of temperatures to whichthe thermostat is subjected, said means comprising a cam anda camfollower, the second fcam follower cooperating with the first camfollower, and means governed by both-of the cam followers forcontrolling said 4 heating fluid pressure control means.

18. In combination a supply main, a return main, radiators between saidmains, a U-tube having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs, one of the legsl beingconnected to the supply main the other of the legs being connected tothe return main, and means for shifting the contacts simultaneously withrespect to the mercury. J

19. In combination a supply main, a return main, radiators between saidmains, a U-tube having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs, one of the legs beingconnected to the supply main, the other of the legs being connected tothe return main, and means forl shifting the contacts simultaneouslywith respect to the mercury, said means comprising a cam and camfollower. v

20. In combination a supply main, a return main, radiators between saidmains, a U-tube having closed legs, a body of mercury in the tubeextending Vinto the legs, contacts in the legs, one of the legs beingconnected to the supply main, the other' of the legs being connected tothe return main, means for shifting the contacts simultaneously withrespect to the mercury, said means comprising a cam and cam follower,and a valve in the supply main controlled by said contacts.

21. In combination a supply main, a return main, radiators between saidmains, a U-tube having closed legs. a body of mercury in the tubeextending into the legs, contacts in the legs, one of the legs beingconnected to the supply main the other of the legs being connected tothe return main, and thermostatically controlled means for shifting thecontacts simultaneously with respect to the mercury.

22. In combination a supply main, a return main, radiators between saidmains, a U-tube having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs,

one of the legs being connected to the supply main and the other of thelegs being connected to the return main, thermostatically controlledmeans for shifting the contacts simultaneously with respect to themercury, and a valve in the supply main controlled by said contacts.

'23. In combination a supply main, a return main, radiators between saidmains, a U-tube having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs,

one of the legs being connected to the supply main and the other of thelegs being connected to the return main, means for shifting the contactssimultaneously with respect to the mercury, and means controlled by saidcontacts for governing the emission of heat at the radiators.

24. In .combination a supply main, a return main, radiators between saidmains, a U-tube having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs, one of the legs beingconnected to the supply main and the other of the legs being connectedto the return main, thermostatic means for shifting the contactssimultaneously with re spect to the mercury, and means controlled bysaid contacts for governing the pressure in the supply main.

25. In combination a supply main. a return main, radiators between saidmains, a U-tuhe having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs, one of the legs beingconnected to the supply main, the other of the legs being connected tothe return main, a thermostat, a cam convtrolled by the thermostat, acam follower, and

means controlled by the cam follower for shlft ing the contactssimultaneously with respect to the mercury.

, 26. In combination a supply main, a returnmain, radiators between saidmains, a U-tube having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs, one of the legs beingAconnected to the supply main, the other of the legs being connected tothe return main, a thermostat, a cam controlled by the thermostat, a camfollower, means controlled by the cam follower for'shifting the contactasimultaneously with respect to the mercury, and means governed by thecontacts for controlling the pressure of heating fluid in the supplymain.

27. In combinationl a supply main, a return main, radiators between saidmains, said radiators having inlet orifices, a U-tube having closedlegs, a body of mercury in the tube extending into the legs, contacts inthe legs, one of the legs being connected to the supply main, the otherof the legs being connected to the return main, a thermostat, a camcontrolled by the thermostat, a cam follower, the relation of throw ofthe lfollower to the motion of the cam embody- V:ing the relation ofpressure difference upon the orifices and the consequent flowtherethrough.

' means controlled by the cam follower for shifting the contactssimultaneously with respect to the mercury, and means governed by saidcontacts for controlling the pressure difference of heating fluid uponsaid orifices.

28. In combination 'a supply main, a return main, radiators between saidmains, a U-tube 4having closed legs, a body of mercury in the tubeextending into the legs, contacts in the legs, one of the legs beingconnected to the supply main, the other of the legs being connected tothe return main, a thermostat, a cam controlled by the thermostat, a camfollower. the relation between the throw of the follower' and the motionof the -cam embodying the relation between pressure of the heating fluidand the heat to be emitted by the radiators, means controlled by the camfollower for shifting the contacts simultaneously with respect to themercury, and means controlled by said contacts for varying the pressureof steam in the supply main.

29. In combination, a supply main, a return main, radiators between saidmains, a movably disposed U-tube having closed legs, a body of mercuryextending into said legs, contact means coo-perating with said tube, oneof said legs being connected to the supply main and the other of saidlegs being connected to said return main, and means for shifting saidcontact means relative to said tube.

30. In combination, a supply main, a return main, radiators between saidmains, a movably disposed balancing device, a body of mercury disposedin said device, contact means cooperating with said balancing device,means for connecting said supply main and said return main to saiddevice, means for shiftingv said contact means relative to said device,said means comprising a cam and a cam follower, and a valve in thesupply main controlled by said contact means.

3l. Incombina'tion, a. supply main, a return main, radiators betweensaid mains, a movably disposed balancing device, a body of mercurydisposed Within said device, contact means cooperating with saidbalancing device, the supply main and the return main being connected tosaid device, thermostatically controlled means for shifting said contactmeans relative to said device, and meanscontrolled by said contact meansfor governing the emission of heat at said radiators.

32. In a system of the class described, a temperature responsive devicefor governing the actuation of heat supply control means for supplyingheating Huid to radiators, a Wheatstone bridge responsive to saiddevice, a movable cam actuated by said Wheatstone bridge, a supply main,a return main, said radiators being disposed between said mains, mercurybalance means, said mains being connected to said mercury balance means,contact means cooperating withv said movable balance means, and meansvincluding said movable cam for actuating said contact means.

33. In a. system of the class described, a temperature responsive devicefor governing the actuation of heat Supply control means for supplyingheating fluid to radiators, a Wheatstonebridge responsive to saiddevice, a movable cam actuated by said Wheatstone bridge, a suppl; main,a return main, said radiators being disposed between said mains, movablymounted mercury balance means, said mains beingV connected to saidmercury balance means, contact means cooperating with said balancemeans, and means including said movable cam for shifting said contactmeans relative to said mercury balance means.

34. In a system of the class described, a temperature responsive devicefor governing the actuation of heat supply control vmeans for supplyingheating iiuid to radiators, a Wheatstone bridge responsive to saiddevice, a movable cam actuated by said Wheatstone bridge, a supply main,a. return main, said radiators being disposed between said mains,movably disposed mercury balance means, said mains being connected tosaid mercury balance means, contact means cooperating with said balancemeans, means including said movable cam for shifting said contact meansrelative to said movably disposed balance means, and means controlled bysaid contact means for governing the emission of heat at said radiators.

35. In a system of the class described, a temperature responsive devicefor governing the actuation of heat supply control means for supplyingheating fluid to radiators, a Wheatstone bridge responsive to saiddevice, a movable cam actuated by said Wheatstone bridge, a supply main,a return main, said radiators being disposed between said mains, movablydisposed balance means, a contact carried thereby, said mains beingconnected to said balance means, other contact means cooperating withthe contact carried by said balance means, means including said movablecam for shifting said other Contact means relative to said Contactcarried by said balance means, and means controlled conjointly by saidcontact and said other contact means for providing the emission of heatat said radiators.

36. In a system for supplying heating Huid to a building at ratesproportional to the dierence between outside temperature and apredetermined temperature which it is desired to maintain in thebuilding, the combination of a thermostat responsive to outsidetemperature, a heating fluid supply means, a Wheatstone bridge having acontroling variable resistance, and a responsive member subject to thevariations of said resistance controlling said heating iiuid supplymeans, saidV controlling variable resistance beingv substantiallyuniformly graduated throughout, andD a cam member movable uniformlyinresponse to the thermostat and acting non-uniformly upon theresistance to vary the same.

37. In a system for supplying heating fluid to a building at ratesproportional to the diference between outside temperature andaipredetermined temperature which it is desired to maintain in thebuilding, the combination of a thermostat responsive to outsidetemperature, a heating fluid supply means, a Wheatstone bridge having acontrolling variable resistance, and a responsive member subject to thevariations of said resistance controlling said-heating fluid supplymeans, said controlling variable resistance being substantiallyuniformly graduated throughout, a cam member movable uniformly inresponse to the thermostat and acting non-uniformly upon the resistanceto vary the same, and a multiplying resistance in shunt of said variableresistance for adjusting the heating rate throughout the temperaturerange of the system.

38. In a steam heating system having a supply line, a pressureregulating valve therein, a return line, andmeans differentiallyresponsive to the steam pressures in said supply line and said returnline for controlling said valve, the combination of a plurality of meansincluding a wind meter, and a. thermally sensitive element jointlyoperative to modify the control of said pressure responsive means uponsaid valve, and electrically operated manual control means forregulating the modifying action of said plurality of means.

'HERBERT G. THOMAS.

